Abstract
Urbanization addresses urban expansion, and it leads conversion of the green space into the built-up area. However, previous studies mainly focused on two-dimensional (2D) urban expansion rather than three-dimensional (3D) growth. Here, the purpose of this study is to examine the urban expansion, including built-up and green space for both horizontal and vertical dimensions using geospatial analysis including remote sensing (RS) and Geographic Information System (GIS) in the sub-Central Business District (CBD) area of Surabaya, Indonesia. The medium resolution remote sensing data for both image and Digital Surface Model (DSM) acquired by Advanced Land-Observing Satellite (ALOS) were applied for time-1 (2010). The orthophoto and DSM derived by LiDAR were used for time-2 (2016). We quantified the built-up and green expansions in 2D (area), which were extracted from land use/land cover (LU/LC) by applying hybrid classification. The built-up and green expansions in 3D (volume) were estimated by generating a surface feature model. The spatial configuration of area expansion was investigated using patch metric, while the volume growth was examined using the volume expansion rate. We got three findings. (1) The built-up and green area had expanded about 11.54% and 95.61%, respectively, from 2010 to 2016. The expansion of green area presented in a notable portion, which was mainly contributed by the conversion of bareland to playground or park. However, the expansion of built-up area was less than the volume expansion of 20.6%. It revealed that built-up growth led to vertical rather than horizontal development. (2) The built-up area expansion tended to scatter configuration, whereas, the green area expansion tended to aggregate in a linear pattern. (3) The ratio of built-up volume expansion to green volume expansion showed a mean of 3.7, indicating that the development of built-up and green volume was imbalanced. The built-up growth presented higher than the green growth, mainly in the areas with more vertical building establishment. The pressing need for higher green volume in the study area was identified in several sites located at surrounding artery and toll roads. Overall, our approach can be applied as a reference in monitoring neighborhood environment through greening programs for sustainable urban development.
Highlights
It is predicted that urban population will gain 66% of the world’s total population by 2050, which means global urbanization, continuing to increase at the current level, especially in developing countries [1]
The expansion of green area presented in a notable portion, which was mainly contributed by the conversion of bareland to playground or park
The geospatial approach was conducted for examining the urban form for bi-temporal (2010–2016) in conjunction with two material aspects and two configuration aspects (2D-3D space and spatial pattern)
Summary
It is predicted that urban population will gain 66% of the world’s total population by 2050, which means global urbanization, continuing to increase at the current level, especially in developing countries [1]. Urbanization is always accompanied by spatial expansion of urban land [2]. In Southeast Asia, the urban expansion rate is approximately 2.8% higher when compared to other urbanized regions of the world [3,4]. Green space had increasing pressure during the urban expansion and caused many serious ecological problems, psychological well-being, and the health of urban dwellers [5]. It is essential to examine and to monitor the change of green space coverage in spatial complexity of the urban landscape when rapid expansion occurs
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